A sheet conveyance device, an image forming apparatus, and a sheet conveying method that convey a sheet in a predetermined sheet conveyance direction make a surface moving speed of a driven roller higher than a surface moving speed of a drive roller when a rotational driving force from the drive roller is transmitted to the driven roller, and by a one-way clutch that is provided at any place in a drive transmission path from the drive roller to the driven roller, restrict relative rotation of the driven roller in a first rotation direction, which is the sheet conveyance direction, with respect to the drive roller while allowing relative rotation of the driven roller in a second rotation direction, which is a direction opposite to the first rotation direction, with respect to the drive roller.

An image forming apparatus includes an image carrier, a transfer member, a registration roller pair, and a conveyance guide. The conveyance guide includes a first conveyance guide which faces an image-carrier-side surface of the recording medium, and a second conveyance guide which faces a transfer-member-side surface of the recording medium. The second conveyance guide has a main body portion which has a projecting portion which projects toward the first conveyance guide most in a recording-medium conveyance path, and a step portion which is formed adjacent to the projecting portion on a downstream side of the projecting portion, an elastic member which projects toward the first conveyance guide beyond a plane passing through a downstream-side end of the projecting portion and a downstream-side end of the step portion, and a film member which covers the main body portion together with the elastic member.

A toner case includes a case main body, a rotator, a transmitter and a cover. The case main body stores a toner. The rotator is stored in the case main body and rotates around a rotation axis. The transmitter transmits rotation to the rotator. At least apart of the transmitter is arranged outside the case main body. The cover moves along a rotation axis direction of the rotator between a covering position where the cover covers an outer circumference of the transmitter and an exposing position where the cover exposes the transmitter.

A motor controller that controls a motor in which a rotor using a permanent magnet is rotated by a rotating magnetic field due to a current flowing through a winding: performs hold control that continuously causes a fixed excitation current to flow through the winding to cause a fixed magnetic field for suppressing rotation of the rotor to be generated in a suspension period in which the motor is stopped; performs hold enhancement control that enhances the fixed magnetic field with input of a timing signal defined in advance as a trigger, in the suspension period; and starts rotational excitation control that generates the rotating magnetic field when a rotation start timing arrives.

A sheet conveyance apparatus includes a first conveyance portion configured to convey a sheet, a second conveyance portion configured to convey the sheet, the second conveyance portion including an abutment portion configured to form a loop on the sheet by being abutted against a leading edge of a sheet conveyed by the first conveyance portion, a curved guide portion, which is curved, configured to guide the sheet conveyed by the first conveyance portion to the second conveyance portion, and a rotary member arranged downstream of the first conveyance portion and upstream of the second conveyance portion in a sheet conveyance direction, and configured to be driven to rotate by a surface of the sheet that is guided by the curved guide portion, the surface sliding against the curved guide portion.

An image forming apparatus includes plural rotating members that are rotatable; an annular circulating member that is wound around the plural rotating members and circulates when the rotating members rotate; a retaining member attached to an attaching portion of the circulating member and that circulates together with the circulating member, the retaining member being configured to retain a recording medium in an area where the attaching portion comes into contact with one of the rotating members; an image forming section that forms an image on the recording medium at an image forming position defined on a circulation path along which the circulating member circulates; a delivering unit that delivers the recording medium to a retaining position where the recording medium is to be retained by the retaining member; a detector that detects rotation of the one rotating member; and a controller that controls delivery of the recording medium from the delivering unit to the retaining position, the delivery being controlled with reference to information detected by the detector.

The image forming apparatus transfers an image onto a surface of a sheet at a transfer position on a conveying path. A pair of conveying rollers convey the sheet to the transfer position. The image sensor reads the sheet upstream of the transfer position. The rotary body is disposed to face the image sensor with the conveying path interposed therebetween. The rotary body includes a background portion configured to face a reading surface of the image sensor when the rotary body is at a first rotational position, and a cleaning portion configured to come into contact with the reading surface of the image sensor when the rotary body is at a second rotational position.

A drive mechanism that drives a rotator to rotate includes a main motor, an assist motor, and processing circuitry. The main motor drives the rotator. The assist motor drives the rotator and assists a drive of the rotator by the main motor. The processing circuitry controls a speed of the main motor so that a rotational speed of the rotator is constant, and controls a motor voltage of the assist motor so that the motor voltage of the assist motor changes according to a change in a motor current of the main motor.

A drive transmission device includes a drive train including a plurality of drive transmitters, and a container. The plurality of drive transmitters of the drive train transmit a driving force of a drive source to a rotator rotatable around a shaft and a swing member rotatable around a shaft different from the shaft of the rotator. The container contains the drive train.

A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.